This invention relates to an electronic musical instrument with touch response function.
An electronic musical instrument having a function of providing a touch response character to each tone generated, is disclosed in, for instance, the specification of Japanese Patent Publication No. 59-2914. In this disclosed electronic musical instrument, each key on a keyboard has a key switch which has first and second fixed contacts and a movable contact. With an on/off operation of a key, on/off data representing the on/off state of the corresponding key switch and time data indicative of whether the movable contact is moving between the first and second fixed contacts, are obtained according to a signal produced from the key switch. A touch response character is produced from the on/off data and time data thus obtained.
In the above prior art electronic musical instrument, however, the on/off data and time data of the key switch are obtained through division of a 3-level analog voltage through a resistive voltage divider in a key switch circuit. In this case, three resistors are employed for each key, and the accuracy of the analog voltage which depends on the accuracy of the resistors is low. Therefore, it is difficult to set accurate threshold values for two buffers, which are provided on the output side of the key switch and have different threshold voltages.
In addition, the individual keys are scanned one after another to obtain a touch response output for each key. Therefore, there is an upper limit on the response speed, and the accuracy of the touch data is too low to obtain a satisfactory touch response.